12ial-Global Hazard Distribution Physical

​Global Hazard Distribution (1.3.2)

By Aimee Cooper

​Describe global patterns of earthquakes, volcanoes, tropical cyclones, and drought.

Explain the physical processes controlling these patterns.

Interpret global maps of hazard occurrence. Apply this knowledge to short written responses.

Open Ended

What is a natural hazard?

What is the Disaster-Risk Equation?

Name one hydro-meteorological hazard.

Name one geophysical hazard.

What human factor increases vulnerability?

​Enquiry Question

​Where and why are natural hazards concentrated in specific parts of the world?

Draw

On a blank world outline, shade and label:

Earthquake zones

Volcanic belts

Tropical cyclone tracks

Drought-prone regions

Use different colours for each.

​If you plotted every major earthquake, volcano, cyclone track, and drought zone on one map, distinct belts would emerge:

Linear chains of earthquakes and volcanoes tracing the world’s plate boundaries.


Broad tropical belts of cyclone activity straddling the Equator.


Vast continental interiors marked by recurrent drought. Only a few regions, such as northern Canada or central Africa, remain relatively hazard-free.

​Earthquakes: Distribution and Cause

​Earthquakes cluster along plate margins where stress builds as plates move.

Destructive (convergent) margins generate the deepest and most powerful events as one plate is forced beneath another. Examples include Japan, Chile, and Indonesia.

Conservative (transform) margins, such as California’s San Andreas Fault, create frequent but shallower shocks.

Constructive (divergent) margins like the Mid-Atlantic Ridge produce smaller quakes as plates pull apart.


Intra-plate events occur within stable continental crust, e.g. the 2001 Gujarat quake in India. These are rare but often unexpected and devastating.

Open Ended

Explain how different plate boundaries can impact the strength of hazards.

​Plate Boundary

​Divergent: shallow quakes, basaltic lava flows.

Convergent: deep quakes, explosive composite volcanoes.

Transform: lateral displacement, frequent shocks.

​Volcanoes: Global Pattern

​Volcanoes occur in similar linear belts but reveal subtle contrasts. About four-fifths of the world’s active volcanoes lie around the Pacific Ring of Fire.

Here, subduction of dense oceanic crust beneath lighter continental plates produces steep-sided, gas-rich composite volcanoes prone to violent eruption.


In contrast, divergent margins such as Iceland or the East African Rift yield broad shield volcanoes with fluid basaltic lava.


A smaller number occur at intra-plate hot-spots, where stationary magma plumes break through the crust — the Hawaiian Islands are the classic example.

Open Ended

Explain why magma composition differs between convergent and divergent settings, and how this affects eruption style.

Open Ended

Describe one continuous volcanic belt and one isolated cluster.
Extension: deduce what this pattern suggests about plate movement and mantle plumes.

​Tropical Cyclones: Global Pattern

​Tropical cyclones (hurricanes, typhoons) are confined to warm ocean belts between about 5° and 20° latitude N and S of the Equator.

They form where: sea-surface temperature exceeds 26 °C, the warm layer extends at least 70 m deep, Coriolis force is strong enough to create rotation, and vertical wind shear is low.


Systems travel westwards with the trade winds then recurve polewards. Major basins include the Western Pacific, North Atlantic, and Indian Ocean.


Why none at the Equator? The Coriolis effect is too weak there to generate rotation.

Open Ended

Questions:

In which oceans are storms most numerous?

Where do most storms lose intensity?

Which coastlines experience repeated landfall?

​Drought Distribution

​Drought predominates in subtropical high-pressure zones where descending dry air suppresses rainfall (roughly 20°–35° latitude).


Continental interiors remote from oceanic moisture, such as central Australia, also experience long dry spells.


In addition, periodic climate oscillations like El Niño–Southern Oscillation (ENSO) cause alternating drought and flood years in many parts of the tropics.

Open Ended

Explain in two sentences how atmospheric circulation and ENSO both influence drought occurrence.

​Multiple Hazard Zones

​Some regions, notably the western Pacific, face overlapping threats: tectonic activity creates quakes and volcanoes while warm seas fuel cyclones.
These ‘multi-hazard environments’ experience compounding impacts when events coincide — for example, an earthquake weakening defences before a typhoon season.

Open Ended

Identify one multi-hazard region on your map and suggest two physical reasons for its complexity.

​Areas of Low Hazard

​Stable continental interiors such as northern Canada, central Asia, or large parts of Europe experience few hazards because they lie far from active plate boundaries, have temperate climates, and lack the heat or humidity needed for cyclone development. Even here, however, drought and flash-flood events may occur intermittently.

Open Ended

If scientists can map hazard zones so clearly, why do disasters still occur?

Open Ended

1 At what sea-surface temperature do cyclones form?
2 Which type of plate margin produces the deepest earthquakes?
3 Roughly what proportion of volcanoes occur around the Pacific Ring of Fire?
4 Why are cyclones absent at the Equator?
5 Give one cause of global drought distribution.

​Produce a one-page illustrated summary that shows: the global pattern of each hazard type, the controlling physical processes, and one named example for each.

​Task

​Describe global patterns of earthquakes, volcanoes, tropical cyclones, and drought.

Explain the physical processes controlling these patterns.

Interpret global maps of hazard occurrence. Apply this knowledge to short written responses.